The present technology relates to a solid-state image sensor and an electronic device, and particularly relates to a solid-state image sensor and an electronic device making it possible to acquire a natural and beautiful image by using an image sensor.
In recent years, a CMOS image sensor has been widely used as an imaging device. However, the CMOS image sensor generally performs reading in sequence for each pixel and thus is not capable of realizing simultaneity in an entire image.
That is, the CMOS image sensor executes an operation in which a photocharge generated by a photoelectric conversion section and stored therein is sequentially scanned and read for each pixel or each line. In the case of the sequential scanning, that is, in the case of employing a rolling shutter as an electronic shutter, exposure for storing the photocharge may be difficult to be started or terminated at the same time in each pixel. Accordingly, when an image of a moving subject is captured, the sequential scanning might disadvantageously result in distortion in the captured image.
Such a type of image distortion is not allowed in image capturing of a subject moving at high speed or in sensing involving simultaneity of image capturing. For these purposes, a global shutter is employed as the electronic shutter, the global shutter executing start or termination of the exposure at the same time for all the pixels in a pixel array.
In an image sensor employing the global shutter as the electronic shutter, a charge storage section using a semiconductor memory, for example, is provided in each pixel. The image sensor employing the global shutter ensures the simultaneity in the entire image in such a manner that charges are transferred at the same time from photodiodes to semiconductor memories, stored in the semiconductor memories, and then read in sequence (for example, see JP 2008-103647A).
In other words, in the case of employing the global shutter in the CMOS image sensor, it is necessary to provide a region where a signal corresponding to a charge obtained by light receiving is stored in a time period from turning off of the shutter to the start of reading the signal. For this reason, reduction of a light receiving area and a storage area involved with the advance of pixel microminiaturization is likely to cause deterioration of sensitivity or a dynamic range.
Hence, there is proposed avoidance or the like of the reduction of the light receiving area or the storage area by using a floating diffusion (FD) as a storage region.
Further, there is also proposed an image sensor including: a floating diffusion FD; and a transistor MT which includes a floating gate (FG) serving as a charge storage section and a gate electrode CG connected to the floating diffusion FD (for example, see JP 2010-226375A). Thereby, the global shutter and the rolling shutter are made mutually compatible and thus the number of transistors provided in a pixel section can be three at the minimum, and microminiaturization of the pixel section, for example, is facilitated.